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# RE: Thick Concrete Walls, no non-linear EQ dissipation

• To: "SEAINT" <seaint(--nospam--at)seaint.org>
• Subject: RE: Thick Concrete Walls, no non-linear EQ dissipation
• From: "David Merrick" <mrkgp(--nospam--at)winfirst.com>
• Date: Tue, 11 Mar 2003 17:39:30 -0800

```Thank you Michael Bryson for the reference PCA publication, "Design and
Control of Concrete Mixtures". I am looking forward to viewing the thermal R
values

I agree that the seismic R=1. The SEAOC blue book table C105-2 clarifies
this. I am considering an Elastic Response VE and in attempting a fully
elastic shearwall system. VS=VM=VE and so Omega then might be 1.0.
.

The actual seismic R value may be higher. I am still using the Omega=2.8. I
found in ASCE 7-02 "...Loads for...Structures" a concrete wall has an R of
4.0 and Wo (similar to Omega) is 2.5. Unlike the UBC it also gives values
for plain masonry R=1.5 and it does not change Wo. It must be best to use
the UBC equations with R=1.0 (almost 1g) and leave Omega as 2.8 (more than
2g). I am not using plain concrete but only a study as to what steel is
required for a non-elastic system.

I will calculate ro redundancy rather than assume the maximum of 1.5.

I have yet to find the 1997 UBC rejecting energy dissipation in the linear
range of response. Section 1921.2.1.1 describes section 1921 to be
specifically for "special requirements for design...earthquake...on the
bases of...energy dissipation in the NON-linear range of response." That
excludes the linear range option for that section only and may be an
advantage. An energy dissipation in the linear range of response then is
still part of other sections in the code, unless I find other forms of
exclusions.

The walls, being so thick, have a savings, in detailing. They will have
reinforcement. Even an Egyptian pyramid would require a minimum of steel,
and of course special inspections.

Comments by others not on this email list were...
*Have not studied that part of the 97 code yet.
*Use base isolation with a polyurethane foundation, be sure to use the
interconnected polymers or else creep continues the life of the voids.
*Cantilever the walls to not rely on a diaphragm. (Flexible diaphragms may
be incompatible with short and fat walls.)
*What do they do with adobe and rammed earth?

Hey Dennis Wish, this approach is something like that for a granite monument
design!

David Merrick, SE

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